In my opinion, when talking about books, it makes more sense to say that its inconsistent characterization than to say that the character is ooc. To me, saying they're ooc implies that they are intentionally or accidentally being something other than themselves, more like an actor or a player in a role playing game doing something they'd do rather than the character they're trying to portray. Inconsistent characterization places the responsibility? i guess for the weirdness on the author rather than the character, which is where it should be.